You always want what you can't have. There are plenty of Tessars for the Contax, but the lens that people want is the Sonnar.
And for the Tenax II, it came with the Sonnar or Tessar, and people want the Sonnar.
Still, there are a lot of cameras out there, prewar, postwar, East German, West German, that have a Tessar. Turn-of-the-century Tessars, 1930s and 1940s Tessars, postwar East German and West German Tessars. Yashica/Kyocera Tessars. And the various copies made by nearly everyone, it seems.
It might be interesting to see a Tessar in ZM mount -- especially if it was a lower-priced alternative to the Planar and Sonnar. However, "lower priced" might not be the bargain-basement price most people expect.